Hit the button to begin grabbing web sites. Grab-a-Site will follow all of the links and get the files and put them in a folder.
The folder will have the same name as the project. If your project is joe.gas, then the folder with the files will be joe\src. If you have Use Domain in Directory turned on, there will be additional folders.
If you have the Grab Status window turned on, you will see the pages that are pending, and how much data has been sent and received, and how many simultaneous connections (Threads) that the program is using.